The paradigm for dengue virus (DENV) transmission is that mosquitoes feed on viremic humans, become systemically infected, and, after a period of incubation, transmit the virus to a different, susceptible human host during a subsequent blood meal. In assessing transmission potential, measurements of mosquito density and behavior are widely used, but comparatively little is known about the human component of transmission. The goal of this project is to examine how human behavioral responses to DENV infection modify the probability of contact with mosquito vectors in different locations and, consequently, the potential contribution to DENV transmission. We propose a unique and innovative study of the behavioral, perceptual, and clinical responses of individuals across the spectrum of dengue illness, including mild and inapparent infections. We hypothesize that individuals with mild or no illness have lower viremias than those with more severe symptoms, but compensate for this apparent disadvantage in transmission potential by exhibiting higher mobility, leading to greater exposure to mosquito vectors. We will rely on a longitudinal febrile surveillance structure tied to a contact cluster study design (coordinated by the Surveillance Core) to prospectively identify viremic individuals. By applying techniques from our multidisciplinary team of social scientists, clinicians, disease ecologist, and statistician (e.g., focus groups, semi-structured interviews, laboratory testing, continuous monitoring of location and temperature), we will address three Specific Aims. In Aim 1 we will describe and quantify the association between perceived disease severity and objectively defined disease classifications (e.g., viremia, AST, WBC, platelet counts, fever, select immunological markers). In Aim 2 we will examine and quantify human behavior change associated with dengue severity, focusing on human movement but including use of anti-pyretics, accessing health care, and other preventive behaviors. In Aim 3 we will quantify individual risk of exposure to Aedes aegypti mosquitoes as a function of movement and disease severity to examine the potential contribution to DENV transmission.